#include <iostream>
using namespace std;
int reverse(int n) {
int t = n;
int count = 0;
while (t) {
count++;
t /= 10;
}
int a[count];
t = n;
for (int i = count - 1; i >= 0; i--) {
a[i] = t % 10;
t /= 10;
}
int res = 0;
for (int i = count - 1; i >= 0; i--) {
res += a[i];
res *= 10;
}
return res / 10;
}
int main() {
int n1, n2;
int r1, r2;
while (cin >> n1 >> n2) {
r1 = n1 + n2;
r2 = reverse(n1) + reverse(n2);
if (r1 == reverse(r2)) {
cout << r1 << endl;
} else {
cout << "NO" << endl;
}
}
}
// 64 位输出请用 printf("%lld")